I used to have a Coke (not even diet) every friggin' day. My one New Year's resolution for 2012 was to "drink less soda" and I ended up almost completely giving it up. (Okay, I still have a Dr. Brown's Black Cherry soda on special occasions.) It's the best thing I've done for myself since I quit smoking. Hang in there, and drink lots of water and iced tea instead!
You can do it!